Aerosol can and piston assembly

ABSTRACT

A cylindrical can having a longitudinal seam presenting higher and lower inwardly projecting portions, and a piston within the can having at least three external ribs. The spacing between each two successive ribs is no greater than the length of one lower seam portion, and the spacing between two alternate ribs is greater than the length of one higher seam portion. The ribs may extend around the entire periphery of the piston or only a portion thereof. The top and side walls of the piston may be provided with inwardly projecting ridges.

United States Patent [1 1 [111 3,

Scheindel Oct. 28, 1975 AEROSOL CAN AND PISTON ASSEMBLY Primary Examiner-Drayton E. Hoffman [76] Inventor: Christian T. Scheindel, Star Rte., Asslsmm Examme'g'gadd Lane Randolph Center Vt 05061 Attorney, Agent, or Firm-Alan H. Levine [21] Appl- 504,461 A cylindrical can having a longitudinal seam presenting higher and lower inwardly projecting portions, and 52 us. Cl. 222/389; 92/242 a Piston Within the can having at lenst three external 51 Int. cm. B67D 5/42 ribs The Spacing between each two Successive ribs is 58 Field of Search 222/389, 386, 386.5; no greater than the length of one lower Seam Portion, 92 20 2 2 240 24 2 243 2 9 and the spacing between two alternate ribs is greater than the length of one higher seam portion. The ribs [56] References Cited may extend around the entire periphery of the piston UNITED STATES PATENTS or only a portion thereof. The top and side walls of the piston may be provided with inwardly projecting 3,132,570 5/1964 Hoffman, Jr. et al 222/389 X ridges 3,381,863 5/1968 Towns 222/389 X l 9 Claims, 6 Drawing Figures I 4 I r I I r v I I a 1 I 5 1 I i u \1 n w I I a I a 1 1 l l r a i US. Patent Oct. 28, 1975 Thisinvention relates to aerosol containers, and

more particularly to'a particular type of seamed canand a pistion'of special character foruse-withthe can.-

Aerosol cans fordispersin'g viscous products, such-as cheese spreads and toothpaste, are commonly provided with a hollow piston'slidable longitudinally within the can. The product to "be dispensed is located above the piston, and a pressurized fluid, such ascompressed air,

fills the space within and below the piston. when the dispensing-valve of the can is opened-the pressurized fluid pushes the piston upwardly in the can 'and the' piston expels some of the'product through the valve.

One type of can'often used as an aerosol container is a three piece can having a meshed seam. The interior of such a canis not perfectly circular because the longitudinal seam of the can projects inwardly from the inner surface'of the 'can 'side wall? Furthe rrnor 'the seam doesfnot project inwardly in aunifdrrn' manner, but instead alternating high and low portions along its length which project toia greater'or lesser extent into the can. The piston is usually made of moldd 'plastic and has a thin flexible side wall which tends to conform to theshape of the inner surface 'of 'the' can side wall when the interior of the piston is pressurized. However, the piston wall is not flexible enough'to confoi'm to the interior shape of the ,can in the region' of theseam. As a result, two spaces usually'res ult between the can and piston walls, one on each side of j 't he' seam. These spaces constitute passages through which the pressurizing fluid beneath the piston canescape past piston into the region of the can containingthe product tob'e dispensed. Such escape of the bid is, of course, disadvantageous since as the pr e' ssiire' lbcrieath the piston is reduced, the ability ofltijie piston t'o push the product out of the valve isredueed, v I

It is an object of the prese'nt invention to, overcome this problem .by providing a can'havinga ,ineshed seam with a piston able to form a seal with theinner surface of the can walLso as topreVent escape of pressurized fluid into the .region of the can filled with the product tobe dispensed. i I

1 It is a more specific object of the invention to provide a piston having a plurality of external ribsso spaced apart that=atleast oneof such ribs is always in engage FIG. 5 is an elevational view of an alternative embodim'ent of a piston accordin'gto thejnvention, and

has a' series of slits extending inwardly from, and .per

pendicular togthe edge, the slits defining. ayserie s. of square'fingers between them-The fingers of the-one edge and ever'yother finger ofztheother edge-are bent back' upon the sheet and the bent-back fingers are inter.- locked. The interlocked fingers produce a bulk result-j in higher portions 13' of the vseam: 11 projecting into the can. Alternating with "the higher portions are. lower portions 14 comprising the unbent square fingers overlapping margin of the 'opposit'e' side-of thepinie tially flat metal sheet. The seam 11 is then' soldered to make it 'fluid tight. T w. Crimped to the'bottom edge of can side wall z-l2e-isi-a bottom wall 17 having a hole through which'a pressurized fluid is introduced into the bottom of-the can after which the hole is closed'by aresilient plug 18.-Cr'imped to the top edge of can sidewall 12 is a top wall 19 have ing a large opening" into which a valve assembly". 20 is seated. The edge of the valve assembly is criniped to the edge surrounding the opening in the' top wall's 'iSlidable longitudinally within'can 10 is-a hollowzpiston 23, preferablvfformed of a molded plastic =s'i1chaas polyethylene, having a flexible sidewall and a top wall 25 The "t'cpwaII-24 isfshaped to cdnform tb the shape of the lower fsurface of top wall 19 and valve assembly2i) so that w en pistiori 23 reaches'thetop of thejcan lilit can expel'all or substantially alIOf the product through "valve assembly 20. I'hregion I 26 within-the can above'pi'ston 23 is filled with the product re be dispensed, and theregion 21; witliinand below pistion 23 is filled with e pressurized fluid, such as comment with a low portion of the meshed can se amto thereby-form a seal with the can wall around the entire periphery of the piston. 1

It is another object of the invention to provide the wall of such a pistion with strengthening ridges, and to provide the side wall of the piston with integrallymolded inwardly projecting ridges to permit the side walls to be as thin and flexible as possible.

Additional objects and features of the invention will be apparent from the following description in which reference is made to the accompanying drawings.

In the drawings:

FIG. 1 is a longitudinal cross sectional view through an aerosol container according to the present invention;

FIG. 2 is a vertical cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is an elevational view of a piston according to the invention;

FIG. 4 is a bottom view of the piston of FIG. 3;

.pressed air.. i I v u As thus fardescribedfthe aerosol container is'cornpletely conventional. 'I-I wevcr, the external surface of side wall 24 of piston is furnis'hed with'at least-three, and preferably fond, ribs 30, 31,32; and 335' Ihe i'ibs extendhorizontally along theperiphi'y of 'tlie 's'ide 'wall 24, i.e., transverse to the longitudinal directidn of seam 1-1,. and are spacedapart'i'along theleng'tli'of the-seam. The spacing b w in the between eachtwo' succe'ssiv ribs, I ribs- '31, is no greater the length,'rne u ed ong le'n' gth of seam 1 1, of one of the lower semi" portions MI -The spacing between any two alternate ribs, i.e., any two ribs on opposite sides of a third rib, e.g., ribs 30 and 32 or ribs 31 and 33, is greater than the length of one of the higher seam portions 13. In this description, each higher seam portion 13 is considered to include the inclined sections 34 on each side of the higher portion which are the transistions between the'higher and lower portions. Thus, the higher seam portions are considerably longer than the lower seam portions.

As a result of the rib spacing described above, at least one of the ribs 30-33 will always be in contact with one of the lower seam portions 14. For example, in FIG. 1, piston 23 is in a position in which rib 30 is in engagement with a lower seam portion 14, ribs 31 and 32 are both in engagement with a higher seam portion 13, and rib 33 is in engagement with another lower seam portion 14. This engagement is permitted due to the flexibility of piston side wall 24. Ribs 31 and 32 can be pushed inwardly without ribs 30 and 33 being pushed in. Due to the engagement of rib 30 with lower seam portion 14, at the level of rib 30 the entire periphery of piston 23 engages the inner surface of the can side wall 12 to form a fluid-tight seal. At the levels of ribs 31 and 32, on the other hand, spaces remain between the piston and can side wall on each side of seam 11. At the level of rib 33, the entire periphery of piston 23 also engages the inner surface of the can side wall. Thus, rib 33, which is not essential, advantageously serves as a second back-up seal to the seal formed in part by rib 30.

As piston 23 moves upwardly in can 10, and rib 30 engages the next higher seam portion 13, rib 31 moves on to the adjacent lower seam portion 14, thereby preserving the seal between the regions 26 and 27 within the can. At no time are more than two of the ribs 30-33 in engagement with higher seam portions 13, and hence at least one rib is always in engagement with a lower seam portion 14.

On its underside, top wall 25 of piston 23 is formed with three radially-extending ridges 37 (see FIGS. 1 and 4) molded integrally with the remainder of the piston. These ridges add rigidity to the relatively thin top wall 24 and insure that the top wall does not collapse downwardly during a step in the can filling operation when suction is applied to the hole in the can bottom wall. Ridges 37 merge into ridges 38 extending downwardlyalong the inner surface of the piston side wall 24. Ridges 38 result from channels provided in the mold in which the piston is formed. The channels permit the molten plastic to flow quickly and evenly, making it possible to mold a thinner wall 24 than could be molded without the channels. A thin wall is, of course, desirable since the thinner the wall the more flexible it is and the more easily it conforms to the inner shape of the can side wall 12.

The piston 23 shown in FIGS. and 6 is identical to piston 23 in most respects, and hence similar parts bear the same reference numerals as parts of piston 23, but followed by a prime. Piston 23', however, is only provided with the minimum three ribs 30', 31, and 32', and each rib extends around the entire periphery of the piston. The advantage of piston 23' is that no care need be taken concerning the angular orientation of the piston when the piston is inserted into can 10, since some part of the ribs will engage can seam 11. in contrast, when piston 23 is assembled with can 10, it must be oriented so that ribs 30-33 engage seam ll.

The invention has been shown and described in preferred form only, and by way of example, and many variations may be made in the invention which will still be comprised within its spirit. It is understood, therefore, that the invention is not limited to any specific form or embodiment insofar as such limitations are included in the appended claims.

What is claimed is:

l. A can and piston assembly, comprising:

a. a cylindrical can having a longitudinal seam projecting into the can interior from the inner surface of the can side wall, said seam having higher portions and lower portions alternating with each other along the length of said seam, and

b. a cylindrical piston within said can having at least three external ribs extending transversely of said can seam and spaced apart along the length of said seam, the spacing between each two successive ones of said ribs being no greater than the length of one of said lower seam portions, and the spacing between any two of said ribs on opposite sides of a third rib being greater than the length of one of said higher seam portions.

2. A can and piston assembly as defined in claim 1 wherein said piston has four external ribs.

3. A can and piston assembly as defined in claim 1 wherein said piston is hollow and defined by a thin flexible side wall merging into a top wall, said ribs projecting from the exterior surface of said side wall.

4. A can and piston assembly as defined in claim 1 wherein said piston has a cylindrical side wall, and said ribs extend along only a portion of the periphery of said side wall, said side wall portion facing said can seam.

S. A can and piston assembly as defined in claim 1 wherein said piston has a cylindrical side wall, and said ribs extend along the entire periphery of said side wall.

6. A can and piston assembly as defined in claim 1 wherein said piston has an integral side and top wall formed of molded plastic, and a radially-extending ridge projecting from the interior surface of said piston top wall.

7. A can and piston assembly as defined in claim 6 including a plurality of said radially-extending ridges.

8. A can and piston assembly as defined in claim 6 including a downwardly-extending ridge projecting from the interior surface of said piston side wall, said downwardly-extending ridge merging into said radiallyextending ridge.

9. A can and piston assembly as defined in claim 8 including a plurality of said radially-extending and downwardly-extending ridges, each radially-extending ridge merging into a downwardly-extending ridge. 

1. A can and piston assembly, comprising: a. a cylindrical can having a longitudinal seam projecting into the can interior from the inner surface of the can side wall, said seam having higher portions and lower portions alternating with each other along the length of said seam, and b. a cylindrical piston within said can having at least three external ribs extending transversely of said can seam and spaced apart along the length of said seam, the spacing between each two successive ones of said ribs being no greater than the length of one of said lower seam portions, and the spacing between any two of said ribs on opposite sides of a third rib being greater than the length of one of said higher seam portions.
 2. A can and piston assembly as defined in claim 1 wherein said piston has four external ribs.
 3. A can and piston assembly as defined in claim 1 wherein said piston iS hollow and defined by a thin flexible side wall merging into a top wall, said ribs projecting from the exterior surface of said side wall.
 4. A can and piston assembly as defined in claim 1 wherein said piston has a cylindrical side wall, and said ribs extend along only a portion of the periphery of said side wall, said side wall portion facing said can seam.
 5. A can and piston assembly as defined in claim 1 wherein said piston has a cylindrical side wall, and said ribs extend along the entire periphery of said side wall.
 6. A can and piston assembly as defined in claim 1 wherein said piston has an integral side and top wall formed of molded plastic, and a radially-extending ridge projecting from the interior surface of said piston top wall.
 7. A can and piston assembly as defined in claim 6 including a plurality of said radially-extending ridges.
 8. A can and piston assembly as defined in claim 6 including a downwardly-extending ridge projecting from the interior surface of said piston side wall, said downwardly-extending ridge merging into said radially-extending ridge.
 9. A can and piston assembly as defined in claim 8 including a plurality of said radially-extending and downwardly-extending ridges, each radially-extending ridge merging into a downwardly-extending ridge. 